1. Field of the Invention
The present invention relates to a method of manufacturing a magnetic head, and more specifically, it relates to a method of manufacturing a rotary magnetic head used in a system like a VCR (Video Cassette Recorder), an R-DAT and the like.
2. Description of the Prior Art
In recent years, with a trend towards high-density recording and wide-band signal processing in a magnetic recording technique, a medium having a high concave force, such as a metal tape and the like, has been used as a recording medium. For this reason, a thin film of a soft magnetic alloy having a high saturation magnetic flux density is used as a core material of a magnetic head. As shown in FIG. 5, for instance, there has been proposed a magnetic head 20 having a soft magnetic alloy thin film 13 sandwiched between nonmagnetic substrates 17.
In a magnetic head 20 having a core of the soft magnetic alloy thin film 13, its track width is defined by the thickness of the thin film 13. With a magnetic head having a track width of 10 .mu.m or under which offers a higher recording density, however, it is difficult to maintain a sufficient core efficiency of its core because the entire core is formed of the thin film 13, which leads to high magnetic reluctance.
As disclosed in Japanese Unexamined Patent Publication No. 33709/1989, the inventors of the present invention have proposed that the thickness of a magnetic head core (i.e., thickness of a soft magnetic alloy thin film) should be so designed to be equivalent to a track width in a gap portion while it should be larger than the track width in any portion away from the gap portion.
FIG. 6 shows a magnetic head 21 disclosed in the above Patent Publication, while FIG. 7 shows a method of manufacturing the same.
In FIGS. 6(a) and 6(b), a soft magnetic alloy thin film 23 has a thickness required for a track width in a gap portion 22 while it is thicker in other portions.
The magnetic head thus structured, as shown in FIGS. 7(a) through 7(h), includes a V-shaped groove 31 formed in a nonmagnetic substrate 27 at a specified pitch. A soft magnetic alloy thin film 23 is formed on an inclined side 29 of the groove 31 to have a larger thickness than that required for obtaining a track width of the magnetic head 21; thereafter, a resist pattern 42 is formed covering the soft magnetic alloy thin film 23 except for a top portion 32 of the V-shaped groove, and an exposed-portion of the soft magnetic alloy thin film 23 is etched to a thickness required for the track width to obtain a body 43. After glass 28 is molded in the body 43, the body 43 is finished into a magnetic head having a tape contact face as shown in FIG. 7(h) by a well-known magnetic head manufacturing process of cutting, shaping, polishing, glass bonding, cylindrical grinding, tape polishing and the like.
However, the photoresist can not be uniformly coated on and adhere to the substrate 27 because it does not assume a plane; thus, there arises the problem that the resist pattern has a poor accuracy.
As a related art, the following conventional embodiments are known: a magnetic head employing a soft magnetic thin film as a core, in which a track width and a rate of a front core thickness to a back core thickness are controlled depending upon a thickness of a film deposited on a substrate, so that a mechanically strong gap is implemented and a decline of a reproducing sensitivity because of a narrowed track is prevented (see Japanese Unexamined Patent Publication No. 80512/1986); a magnetic head which is so configured that a track width is smaller in size than a core thickness in order to increase a sectional area of a magnetic metal of a back core, whereby an increase in magnetic reluctance because of a narrowed track width is eased (see Japanese Unexamined Patent Publication No. 113909/1989); a magnetic head in which a surface portion of a tape sliding face is made simply of a magnetic substance, a track width in a gap portion is determined depending upon a nonmagnetic substance, and a width of a core formed of laminated film of magnetic films and nonmagnetic films is made thicker than the track width in the gap portion, so that magnetic reluctance of the core is reduced to enhance a reproducing efficiency (see Japanese Unexamined Patent Publication No. 211309/1989); a method of manufacturing a magnetic head, in which a core thickness in a portion other than a portion near a gap is made larger than a track width, so that a magnetic reluctance is reduced to enhance a recording/reproducing efficiency (see Japanese Unexamined Patent Publication No. 235011/1989); and a magnetic head in which a core thickness on the back side is made twice or more as large as a core thickness on the front side, so that a gap and a track are narrowed to improve an electromagnetic transducing property and a recording/reproducing property (see Japanese Unexamined Patent Publication No. 40117/1990).